I've been told recently that when you delete files they are not truely and completely deleted. Is this true? And, if so, is there a way to permenately delete files?

Yes, files are not deleted completely. Actually deleting means removing the information regarding the file pointers. The file remains in the hard disk but hidden from our view. This file location once overwritten by any other file then the retrieval becomes difficult and the file cannot be retrieved. But it is totally dependent upon the OS when the file location is getting overwritten. So we cannot wait for that isn't it?? So for permanent removal of files we use an application known as "file shredder". Try to find it out more about this type of application.